/* memchr (str, ch, n) -- Return pointer to first occurrence of CH in the

   first N bytes of STR.

   For Motorola 68000.

   Copyright (C) 1999-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Andreas Schwab <schwab@gnu.org>.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library.  If not, see

   <http://www.gnu.org/licenses/>.  */

#include <sysdep.h>

#include "asm-syntax.h"

	TEXT

ENTRY(__memchr)

	/* Save the callee-saved registers we use.  */

#ifdef __mcoldfire__

	movel	R(d2),MEM_PREDEC(sp)

	cfi_adjust_cfa_offset (4)

	movel	R(d3),MEM_PREDEC(sp)

	cfi_adjust_cfa_offset (4)

	movel	R(d4),MEM_PREDEC(sp)

	cfi_adjust_cfa_offset (4)

	cfi_rel_offset (R(d2), 8)

	cfi_rel_offset (R(d3), 4)

	cfi_rel_offset (R(d4), 0)

#else

	moveml	R(d2)-R(d4),MEM_PREDEC(sp)

	cfi_adjust_cfa_offset (3*4)

	cfi_rel_offset (R(d2), 0)

	cfi_rel_offset (R(d3), 4)

	cfi_rel_offset (R(d4), 8)

#endif

	/* Get string pointer, character and length.  */

	movel	MEM_DISP(sp,16),R(a0)

	moveb	MEM_DISP(sp,23),R(d0)

	movel	MEM_DISP(sp,24),R(d4)

	/* Check if at least four bytes left to search.  */

#ifdef __mcoldfire__

	subql	#4,R(d4)

	bcs	L(L6)

	addql	#4,R(d4)

#else

	moveql	#4,R(d1)

	cmpl	R(d1),R(d4)

	bcs	L(L6)

#endif

	/* Distribute the character to all bytes of a longword.  */

	movel	R(d0),R(d1)

	lsll	#8,R(d1)

	moveb	R(d0),R(d1)

	movel	R(d1),R(d0)

	swap	R(d0)

	movew	R(d1),R(d0)

	/* First search for the character one byte at a time until the

	   pointer is aligned to a longword boundary.  */

	movel	R(a0),R(d1)

#ifdef __mcoldfire__

	andl	#3,R(d1)

#else

	andw	#3,R(d1)

#endif

	beq	L(L1)

	cmpb	MEM(a0),R(d0)

	beq	L(L9)

	addql	#1,R(a0)

	subql	#1,R(d4)

	beq	L(L7)

#ifdef __mcoldfire__

	subql	#3,R(d1)

#else

	subqw	#3,R(d1)

#endif

	beq	L(L1)

	cmpb	MEM(a0),R(d0)

	beq	L(L9)

	addql	#1,R(a0)

	subql	#1,R(d4)

	beq	L(L7)

#ifdef __mcoldfire__

	addql	#1,R(d1)

#else

	addqw	#1,R(d1)

#endif

	beq	L(L1)

	cmpb	MEM(a0),R(d0)

	beq	L(L9)

	addql	#1,R(a0)

	subql	#1,R(d4)

	beq	L(L7)

L(L1:)

	/* Load the magic bits.  Unlike the generic implementation we can

	   use the carry bit as the fourth hole.  */

	movel	#0xfefefeff,R(d3)

      /* We exit the loop if adding MAGIC_BITS to LONGWORD fails to

	 change any of the hole bits of LONGWORD.

	 1) Is this safe?  Will it catch all the zero bytes?

	 Suppose there is a byte with all zeros.  Any carry bits

	 propagating from its left will fall into the hole at its

	 least significant bit and stop.  Since there will be no

	 carry from its most significant bit, the LSB of the

	 byte to the left will be unchanged, and the zero will be

	 detected.

	 2) Is this worthwhile?  Will it ignore everything except

	 zero bytes?  Suppose every byte of LONGWORD has a bit set

	 somewhere.  There will be a carry into bit 8.	If bit 8

	 is set, this will carry into bit 16.  If bit 8 is clear,

	 one of bits 9-15 must be set, so there will be a carry

	 into bit 16.  Similarly, there will be a carry into bit

	 24.  If one of bits 24-31 is set, there will be a carry

	 into bit 32 (=carry flag), so all of the hole bits will

	 be changed.

	 3) But wait!  Aren't we looking for C, not zero?

	 Good point.  So what we do is XOR LONGWORD with a longword,

	 each of whose bytes is C.  This turns each byte that is C

	 into a zero.  */

	/* Still at least 4 bytes to search?  */

	subql	#4,R(d4)

	bcs	L(L6)

L(L2:)

	/* Get the longword in question.  */

	movel	MEM_POSTINC(a0),R(d1)

	/* XOR with the byte we search for.  */

	eorl	R(d0),R(d1)

	/* Add the magic value.  We get carry bits reported for each byte

	   which is not C.  */

	movel	R(d3),R(d2)

	addl	R(d1),R(d2)

	/* Check the fourth carry bit before it is clobbered by the next

	   XOR.  If it is not set we have a hit.  */

	bcc	L(L8)

	/* We are only interested in carry bits that change due to the

	   previous add, so remove original bits.  */

	eorl	R(d1),R(d2)

	/* Now test for the other three overflow bits.

	   Set all non-carry bits.  */

	orl	R(d3),R(d2)

	/* Add 1 to get zero if all carry bits were set.  */

	addql	#1,R(d2)

	/* If we don't get zero then at least one byte of the word equals

	   C.  */

	bne	L(L8)

	/* Still at least 4 bytes to search?  */

	subql	#4,R(d4)

	bcs	L(L6)

	/* Get the longword in question.  */

	movel	MEM_POSTINC(a0),R(d1)

	/* XOR with the byte we search for.  */

	eorl	R(d0),R(d1)

	/* Add the magic value.  We get carry bits reported for each byte

	   which is not C.  */

	movel	R(d3),R(d2)

	addl	R(d1),R(d2)

	/* Check the fourth carry bit before it is clobbered by the next

	   XOR.  If it is not set we have a hit.  */

	bcc	L(L8)

	/* We are only interested in carry bits that change due to the

	   previous add, so remove original bits */

	eorl	R(d1),R(d2)

	/* Now test for the other three overflow bits.

	   Set all non-carry bits.  */

	orl	R(d3),R(d2)

	/* Add 1 to get zero if all carry bits were set.  */

	addql	#1,R(d2)

	/* If we don't get zero then at least one byte of the word equals

	   C.  */

	bne	L(L8)

	/* Still at least 4 bytes to search?  */

	subql	#4,R(d4)

	bcc	L(L2)

L(L6:)

	/* Search one byte at a time in the remaining less than 4 bytes.  */

#ifdef __mcoldfire__

	addql	#4,R(d4)

#else

	andw	#3,R(d4)

#endif

	beq	L(L7)

	cmpb	MEM(a0),R(d0)

	beq	L(L9)

	addql	#1,R(a0)

#ifdef __mcoldfire__

	subql	#1,R(d4)

#else

	subqw	#1,R(d4)

#endif

	beq	L(L7)

	cmpb	MEM(a0),R(d0)

	beq	L(L9)

	addql	#1,R(a0)

#ifdef __mcoldfire__

	subql	#1,R(d4)

#else

	subqw	#1,R(d4)

#endif

	beq	L(L7)

	cmpb	MEM(a0),R(d0)

	beq	L(L9)

L(L7:)

	/* Return NULL.  */

	clrl	R(d0)

	movel	R(d0),R(a0)

#ifdef __mcoldfire__

	movel	MEM_POSTINC(sp),R(d4)

	cfi_remember_state

	cfi_adjust_cfa_offset (-4)

	cfi_restore (R(d4))

	movel	MEM_POSTINC(sp),R(d3)

	cfi_adjust_cfa_offset (-4)

	cfi_restore (R(d3))

	movel	MEM_POSTINC(sp),R(d2)

	cfi_adjust_cfa_offset (-4)

	cfi_restore (R(d2))

#else

	moveml	MEM_POSTINC(sp),R(d2)-R(d4)

	cfi_remember_state

	cfi_adjust_cfa_offset (-3*4)

	cfi_restore (R(d2))

	cfi_restore (R(d3))

	cfi_restore (R(d4))

#endif

	rts

	cfi_restore_state

L(L8:)

	/* We have a hit.  Check to see which byte it was.  First

	   compensate for the autoincrement in the loop.  */

	subql	#4,R(a0)

	cmpb	MEM(a0),R(d0)

	beq	L(L9)

	addql	#1,R(a0)

	cmpb	MEM(a0),R(d0)

	beq	L(L9)

	addql	#1,R(a0)

	cmpb	MEM(a0),R(d0)

	beq	L(L9)

	addql	#1,R(a0)

	/* Otherwise the fourth byte must equal C.  */

L(L9:)

	movel	R(a0),R(d0)

#ifdef __mcoldfire__

	movel	MEM_POSTINC(sp),R(d4)

	cfi_adjust_cfa_offset (-4)

	cfi_restore (R(d4))

	movel	MEM_POSTINC(sp),R(d3)

	cfi_adjust_cfa_offset (-4)

	cfi_restore (R(d3))

	movel	MEM_POSTINC(sp),R(d2)

	cfi_adjust_cfa_offset (-4)

	cfi_restore (R(d2))

#else

	moveml	MEM_POSTINC(sp),R(d2)-R(d4)

	cfi_adjust_cfa_offset (-3*4)

	cfi_restore (R(d2))

	cfi_restore (R(d3))

	cfi_restore (R(d4))

#endif

	rts

END(__memchr)

weak_alias (__memchr, memchr)

libc_hidden_builtin_def (memchr)